Mercedes sell a 60 or 70 degree thermostat for these engines, I believe its for cars running in the arid sahara desert.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

yes thats what i have in the car, just took it for an extended road test and it stayed at 60-70C the whole trip. The car runs wonderfully

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

Well, it is of course your car and the thermostat is your prerogative but I do not think that is the optimum operating temp for the efficiency of that engine. (Power/economy).

I think I need this. Has anyone driven a SDL thru desert at 115+ deg F outside? The temp gauge was reaching 120 deg C, the red zone. It did not kill the head but very close to it. I needed to rig up the aux fan to be turned on all the time to get me home.

So if the engine is running at 90-95C during normal traffic then it may not survive a trip to Death Valley. I believe it should be < 85C under normal traffic. Anything more than that indicates the cooling system is not as efficient as it should be.

My $0.02.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.